From mboxrd@z Thu Jan  1 00:00:00 1970
From: Peter Zijlstra <a.p.zijlstra@chello.nl>
Subject: Re: [PATCH v1 1/5] perf: add context parameter to perf_event
 overflow handler
Date: Fri, 03 Jun 2011 16:41:55 +0200
Message-ID: <1307112115.2353.3392.camel@twins>
References: <1305129333-7456-1-git-send-email-avi@redhat.com>
	 <1305129333-7456-2-git-send-email-avi@redhat.com>
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Cc: linux-kernel@vger.kernel.org, kvm@vger.kernel.org,
	Ingo Molnar <mingo@elte.hu>,
	Arnaldo Carvalho de Melo <acme@ghostprotocols.net>
To: Avi Kivity <avi@redhat.com>
Return-path: <linux-kernel-owner@vger.kernel.org>
In-Reply-To: <1305129333-7456-2-git-send-email-avi@redhat.com>
Sender: linux-kernel-owner@vger.kernel.org
List-Id: kvm.vger.kernel.org

On Wed, 2011-05-11 at 11:55 -0400, Avi Kivity wrote:
> +++ b/include/linux/perf_event.h
> @@ -709,7 +709,9 @@ struct perf_buffer {
>  
>  struct perf_sample_data;
>  
> -typedef void (*perf_overflow_handler_t)(struct perf_event *, int,
> +typedef void (*perf_overflow_handler_t)(void *context,
> +                                       struct perf_event *event,
> +                                       int,
>                                         struct perf_sample_data *,
>                                         struct pt_regs *regs);
>  
> @@ -855,6 +857,7 @@ struct perf_event {
>         u64                             id;
>  
>         perf_overflow_handler_t         overflow_handler;
> +       void                            *overflow_handler_context;
>  
>  #ifdef CONFIG_EVENT_TRACING
>         struct ftrace_event_call        *tp_event; 

If you're adding a pointer here, then why pass it along in the callback
thing if it already has the perf_event *?

It seems to me the callback can easily do
event->overflow_handler_context if it needs the thing.